1. Field of the Invention
The present invention relates to a device for switching optical fibers. More specifically, the present invention relates to a switching device for use with optical fiber which provides improved switching accuracy and without the problem of mechanical distortions.
In the conventional optical fiber switch, a circularity driving and switching method is used. Currently, a commercialized product of such switch has been manufactured by DICON and AOI, etc.
A prior art structure of the optical fiber switch used by DICON and AOI is described with FIG. 1 as follows: A stepping motor can rotate to drive the optical fibers fixed thereon. One end of the optical fiber is connected with a light source through a connector. While the other end of the optical fiber and an end surface of an optical fiber fixed to the fixture are aligned to form into a coupling channel. And the two end surfaces of the two optical fibers are aligned to face a common plane along a central point.
Although the aforesaid optical fiber switch has a high percentage of share so far, it still has some drawbacks. For instance, when the optical fiber fixed to the motor turns at the largest angle, the optical fiber might be damaged or twisted as a result of the mechanical tension. That is the light loss will be increased, or the collimation coupling between two optical fibers will be poor. Such drawbacks will limit the number of optical channels that can be switched. Generally, when the number of optical channels is over 48 channels, the aforesaid drawbacks will emerge. In order to overcome the aforesaid drawbacks of the optical fibers caused by mechanical torsion, the optic-and-mechanical structure must be designed into a two stage in parallel method. This might improve the aforesaid drawbacks, but it will cause more costs on manufacturing the optical channels and the mechanical and electric structure; eventually, it will lost the commercial competitions, such as low cost and simplicity, etc.
U.S. Pat. No. 5,420,946, herein incorporated by reference, describes an optical coupling device which the input fibers is optically aligned with one of a plurality of output fibers via a reflector. The aforesaid reference taught a very different optical coupling switch from the present invention. In the present invention, we use an optical fiber on the fixture to connect to a non-rotatable optical fiber via a rotatable optical fiber. The optical fiber and the supporting stepping motor spindle are optically and mechanically calibrated such what the opposing ends of the non-rotatable and rotatable optical fibers are linearly aligned to allow such optical switching. The reference is totally absent abort the rotatable optical fiber.
In addition to the use of a reflector for light coupling, in the optical coupling device taught by Tsai, GRIN (grade refractive index) lenses--which enlarge the emitted light beam, are used as an aid in aligning the light beams. The light path (as shown in FIG. 7 of Tsai) requires that the distance between the GRIN lens 16 and the reflector 124, and that between the reflector and the output optical fiber 60 be constant. No such constraint is required in the present invention. But more importantly, the present invention provides a totally different mechanism from the Tsai device for optical coupling.